US5777973A - Reproducing and recording optical pickup compatible with discs having different thicknesses - Google Patents

Reproducing and recording optical pickup compatible with discs having different thicknesses Download PDF

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Publication number
US5777973A
US5777973A US08/761,826 US76182696A US5777973A US 5777973 A US5777973 A US 5777973A US 76182696 A US76182696 A US 76182696A US 5777973 A US5777973 A US 5777973A
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US
United States
Prior art keywords
light
disc
reproducing
optical pickup
thickness
Prior art date
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Expired - Fee Related
Application number
US08/761,826
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English (en)
Inventor
Jang-hoon Yoo
Chong-sam Chung
Chul-woo Lee
Kyung-hwa Rim
Kun-ho Cho
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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Filing date
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Assigned to SAMSUNG ELECTRONICS CO., LTD. reassignment SAMSUNG ELECTRONICS CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CHO, KUN-HO, CHUNG, CHONG-SAM, LEE, CHUL-WOO, RIM, KYUNG-HWA, YOO, JANG-HOON
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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1353—Diffractive elements, e.g. holograms or gratings
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/131—Arrangement of detectors in a multiple array
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/13—Optical detectors therefor
    • G11B7/133—Shape of individual detector elements
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G11B7/1367—Stepped phase plates
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B2007/0003—Recording, reproducing or erasing systems characterised by the structure or type of the carrier
    • G11B2007/0006—Recording, reproducing or erasing systems characterised by the structure or type of the carrier adapted for scanning different types of carrier, e.g. CD & DVD
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1372—Lenses
    • G11B2007/13727—Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
    • G11B7/0037—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with discs
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0908—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only
    • G11B7/0909—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for focusing only by astigmatic methods

Definitions

  • the present invention relates to an optical pickup for reading and writing information by scanning an optical recording medium with an optical beam, and more particularly, to a reproducing and recording optical pickup compatible with discs having different thicknesses.
  • An optical recording medium for storing data is mainly of the disc-type, for example, a compact disc.
  • a disc is comprised of a plastic or glass substrate which is transparent to incident light and having a predetermined thickness, and a recording plane coated on the substrate, on which information is recorded.
  • the light is focused by an objective lens of the optical pickup to pass through the substrate of the disc, thereby being refracted.
  • the refracted light reaches the recording plane and is then reflected from the recording plane to the optical pickup.
  • the diameter of the spot is generally proportional to a numerical aperture (NA) of the objective lens and is inversely proportional to a wavelength of the light.
  • NA numerical aperture
  • the objective lens having a large NA drastically increases the spot aberration on the recording plane when the disc is not directly perpendicular to the beam.
  • the tilt allowance of the disc should be controlled more precisely.
  • the substrate is made thin so as to increase the tilt allowance of the high-density disc. Accordingly, as a high-density disc, a digital video disc having a substrate thickness of 0.6 mm has come about, in lieu of the conventional compact disc having a substrate thickness of 1.2 mm.
  • U.S. Pat. No. 5,281,797 by Tatsuno et al. teaches a technology of adjusting the numerical aperture (NA) of an objective lens by a plate having two apertures of different diameters, a diaphragm for use in a camera, or a liquid crystal device (LCD).
  • NA numerical aperture
  • LCD liquid crystal device
  • complex devices are necessary for driving the same mechanically.
  • the device is simply driven by electrical signals.
  • the LCD cannot attain reliability for an extended period of time.
  • two objective lenses optimized depending on the disc thickness may be alternatively used, but such a technique is not desirous as the objective lenses are required to be mechanically driven.
  • NA numerical aperture
  • an optical pickup having a light source, an objective lens for focusing the light generated from the light source onto a disc and a photodetector for detecting a signal by receiving the light reflected from the disc.
  • the optical pickup is for recording or reproducing information and comprises a transparent plate having a central portion formed with a diffraction grating pattern for diffracting a first portion of light travelling from the light source through the diffraction grating pattern to the objective lens, and a transparent portion through which a second portion of light from the light source passes, wherein a zero-order transmitted light separated by the diffraction grating pattern (the diffracted light) and the light passing through the transparent portion are focused onto the disc by the objective lens if the disc is a thin disc, and a positive first-order diffracted light separated by the diffraction grating pattern is focused onto the disc by the objective lens if the disc is a thick disc.
  • a beam splitter may be provided in the optical path between the light source and the objective lens, for splitting the light path of incident light travelling from the light source toward the objective lens in the optical path, wherein the transparent plate having the diffraction grating pattern is disposed in the optical path between the light source and the beam splitter.
  • the present invention may be constructed such that a separate diffraction grating is provided between the objective lens and the transparent plate, for diffracting the light transmitted via the transparent plate into a zero-order light and positive and negative first-order diffracted lights, wherein the photodetector includes first and second light receiving portions for receiving the reflected lights of the zero-order transmitted light being reflected from the discs having different thicknesses, respectively, and third and fourth light receiving portions for receiving the positive and negative first-order diffracted lights.
  • FIG. 1 is a schematic diagram illustrating an optical structure of a reproducing and recording optical pickup compatible with discs having different thicknesses according to an embodiment of the present invention
  • FIG. 2 is a profile showing a light path for a transparent plate shown in FIG. 1 having a diffraction grating pattern
  • FIG. 3 is a detailed plan view of a photodetector shown in FIG. 1;
  • FIG. 4 is a schematic diagram illustrating the optical structure of a reproducing and recording optical pickup compatible with discs having different thicknesses according to a second embodiment of the present invention
  • FIG. 5 is a profile showing a light path for a diffraction grating shown in FIG. 4;
  • FIG. 6 is a detailed plan view of a photodetector shown in FIG. 4.
  • reference numeral 1 denotes a light source
  • reference numeral 2 denotes a transparent plate having a diffraction grating pattern 3 (see FIG. 2)
  • reference numeral 4 denotes a beam splitter
  • reference numeral 5 denotes an objective lens
  • reference numerals 6 and 7 denote thin and thick discs, respectively
  • reference numeral 8 denotes an astigmatism lens
  • reference numeral 9 denotes a photodetector
  • reference numeral 10 denotes a controller
  • reference numeral 11 denotes an actuator for the objective lens 5.
  • the two discs 6 and 7 have different thicknesses, either of which may be placed in an optical reproducing/recording device.
  • the high-density thin disc 6 is a 0.6 mm thick digital video disc
  • the thick disc 7 is a 1.2 mm thick compact disc.
  • a laser diode for emitting a laser beam is employed as the light source 1.
  • the light emitted from the light source 1 passes through the transparent plate 2, reflected by the beam splitter 4 and focused onto either of the discs 6 and 7 by the objective lens 5.
  • the light reflected from the one of the discs 6 and 7 placed in the optical reproducing/recording device passes back through the objective lens 5 and through the beam splitter 4, and is received in the photodetector 9 via the astigmatism lens 8.
  • the photodetector 9 detects signals for reproducing the information recorded on the disc 6 (7) and signals indicative of focus and track positions of the objective lens 5 with respect to the respective disc 6 (7), to then transmit the same to the controller 10.
  • the controller 10 operates the actuator 11 to adjust the focus and compensate for tracking errors of the objective lens 5 in accordance with the transmitted signals.
  • the transparent plate 2 has a diffraction grating pattern 3 engraved in the center thereof, as shown in FIG. 2.
  • the diffraction grating pattern 3 of the transparent plate 2 diffracts the incident light 12 into a zero-order transmitted light 14 and a positive first-order diffracted light 15.
  • the diffraction grating pattern 3 is manufactured as a serration-type, as shown in FIG. 2 to increase light efficiency.
  • the zero-order transmitted light 14 and the positive first-order diffracted light 15 can be separated by the serration-type diffraction grating pattern 3 such that the amount of the zero-order transmitted light 14 and the positive first-order diffracted light 15 are 40% of the original light intensity, respectively.
  • the useless negative first-order diffracted light (not shown) can be reduced to less than 5%.
  • the zero-order transmitted light 14 travels along its original direction to then be focused onto the thin disc 6 by the objective lens 5, together with the light 13 passing through the far-axis portion.
  • the positive first-order diffracted light 15 is also focused onto the thick disc 7 by the objective lens 5.
  • an aberration-corrected spot is formed on the thick disc 7.
  • the emitting angles of the zero-order transmitted light 14 and the light 13 of the far-axis portion do not change. Therefore, the very small spot formed on the thin disc 6 is formed along the optical axis of the objective lens 5.
  • the emitting angle of the positive first-order diffracted light 15 is slightly changed, the spot on the thick disc 7 is spaced slightly apart from the optical axis of the objective lens 5 (see FIG. 1).
  • FIG. 3 is a plan view of the photodetector 9 shown in FIG. 1.
  • the photodetector 9 includes a first light receiving portion 16 and a second light receiving portion 17.
  • the first and second light receiving portions 16 and 17 are divided into four regions A-D and E-H, respectively.
  • the first light receiving portion 16 is formed at a position coinciding with the central axis of the objective lens 5 so as to receive light reflected from the thin disc 6, and the second light receiving portion 17 is formed next to the first light receiving portion 16 so as to receive light reflected from the thick disc 7. Therefore, when using the thin or thick discs 6 or 7, the respective reproduction signals and signals indicative of each focus and track position are calculated from the first light receiving portion 16 and the second light receiving portion 17 of the photodetector 9, respectively as follows.
  • S a through S h are signals output from the divided regions A through H, respectively.
  • the focus and tracking error signals are transmitted to the controller 10 (FIG. 1), which in turn operates the actuator 11 so that the vertical and horizontal positions of the objective lens 5 are controlled according to the focus and tracking error signals.
  • FIG. 4 in which like reference numerals shown in FIG. 1 indicate like elements, illustrates the reproducing and recording optical pickup compatible with discs having different thicknesses according to a second embodiment of the present invention, which is constructed to detect a track servo signal using three beams.
  • a diffraction grating 18 between the transparent plate 2 and the beam splitter 4, and a photodetector 9' further includes third and fourth light receiving portions 19 and 20, as shown in FIG. 6.
  • the diffraction grating 18 is unevenly shaped and diffracts incident light into a zero-order transmitted light 21 and positive and negative first-order diffracted lights 22 and 23. Therefore, the objective lens 5 shown in FIG.
  • each reflected light beam of the zero-order transmitted light 21 is received in either the first and second light receiving portions 16 and 17 of the photodetector 9' depending on which disc 6, 7 is placed in the optical recording/reproducing device, and each reflected light of the positive and negative first-order diffracted lights 22 and 23 is received in the third and fourth light receiving portions 19 and 20, respectively.
  • the reproduction signals and focus error signals operate in the same manner as described above, and the track error signal S7 operates as follows:
  • S i and S j are detection signals of the third and fourth light receiving portions 19 and 20, respectively.
  • the operation circuit can be commonly used in detecting tracking error signals for a track servo, thereby simplifying the circuitry and servo.
  • a transparent plate having a diffraction grating formed on a part thereof is employed, thereby providing a simplified and optically stable optical pickup, in contrast to the conventional optical pickup which drives a diaphragm.
  • the optical pickup according to the present invention has a higher light efficiency than the conventional one using a hologram lens.
  • the detection of the reproduction signals without interference from each other is possible. Also, the focus and tracking errors for the respective discs can be detected precisely, irrespective of the disc thickness, to provide for a stable operation.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Length Measuring Devices By Optical Means (AREA)
US08/761,826 1995-12-07 1996-12-06 Reproducing and recording optical pickup compatible with discs having different thicknesses Expired - Fee Related US5777973A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1019950047452A KR100269105B1 (ko) 1995-12-07 1995-12-07 두께가다른디스크의호환이가능한기록재생용광픽업
KR1995-47452 1995-12-07

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US5777973A true US5777973A (en) 1998-07-07

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US08/761,826 Expired - Fee Related US5777973A (en) 1995-12-07 1996-12-06 Reproducing and recording optical pickup compatible with discs having different thicknesses

Country Status (8)

Country Link
US (1) US5777973A (de)
EP (1) EP0777221B1 (de)
JP (1) JP3043287B2 (de)
KR (1) KR100269105B1 (de)
CN (1) CN1077999C (de)
DE (1) DE69629899T2 (de)
MY (1) MY117678A (de)
TW (1) TW419103U (de)

Cited By (16)

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US5909424A (en) * 1996-02-14 1999-06-01 Samsung Electronics Co., Ltd. Optical pickup device and method to read from and record information to disks of different thicknesses
US6181667B1 (en) * 1997-03-14 2001-01-30 Sanyo Electric Co., Ltd. Optical pickup apparatus capable of suppressing offset of a tracking error signal
US6259668B1 (en) 1996-02-14 2001-07-10 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US20020024917A1 (en) * 1997-03-28 2002-02-28 Samsung Electronics Co., Ltd Optical pickup compatible with a digital versatile disk and a recordable compact disk using a holographic ring lens
US6552990B1 (en) * 1996-10-31 2003-04-22 Sanyo Electric Co., Ltd. Optical head for two different disk thicknesses with a light beam diameter control device
US20030147331A1 (en) * 2002-02-07 2003-08-07 G-Bond Optoelectronics, Inc. Optical pickup diffracting one of two laser beams to a single detector
US6639889B1 (en) 1997-02-13 2003-10-28 Samsung Electronics Co., Ltd. Recording/reproducing apparatus including an optical pickup having an objective lens compatible with a plurality of optical disk formats
US20040032815A1 (en) * 2002-06-05 2004-02-19 Samsung Electronics Co., Ltd Compatible optical pickup
US6791933B1 (en) 1996-08-29 2004-09-14 Samsung Electronics Co., Ltd. Optical pickup using an optical phase plate
US20040264316A1 (en) * 2003-06-25 2004-12-30 Funai Electric Co., Ltd. Optical pickup device
US20050117497A1 (en) * 2002-02-26 2005-06-02 Matsushita Electric Industrial Co., Ltd. Optical element and optical head device using it and optical information device using this optical head device, and computer, optical disk player car navigation system, optical disk recorder and optical disk server using this optical information device
US20080285419A1 (en) * 2007-05-18 2008-11-20 Samsung Electronics Co., Ltd. Hologram optical device, and compatible optical pickup having the hologram optical device and optical information storage medium system employing the compatible optical pickup
US20140245331A1 (en) * 2013-02-25 2014-08-28 Toshiba Samsung Storage Technology Korea Corporation Beam controlling method and optical pickup device for performing the method
US20150154987A1 (en) * 2013-12-03 2015-06-04 HGST Netherlands B.V. Magnetic head having a short yoke with a tapered coil structure
US9159350B1 (en) * 2014-07-02 2015-10-13 WD Media, LLC High damping cap layer for magnetic recording media
US9886977B1 (en) 2016-12-22 2018-02-06 Western Digital Technologies, Inc. Dual cap layers for heat-assisted magnetic recording media

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JPH09282699A (ja) * 1996-04-17 1997-10-31 Nec Corp ２焦点光ヘッド装置
KR100341335B1 (ko) * 2000-05-18 2002-06-22 윤종용 광디스크 플레이어 및 그 기록 또는 재생방법
WO2002049024A1 (en) * 2000-12-11 2002-06-20 Koninklijke Philips Electronics N.V. Device for reading and/or writing a record carrier
JP3772851B2 (ja) 2003-03-28 2006-05-10 ソニー株式会社 光ピックアップ装置及び光ディスク装置
KR100546351B1 (ko) * 2003-07-25 2006-01-26 삼성전자주식회사 호환형 광픽업 및 이를 채용한 광 기록 및/또는 재생기기
KR100924876B1 (ko) * 2005-10-28 2009-11-02 미쓰비시덴키 가부시키가이샤 회절 광학 소자, 및 광 헤드 장치
KR101133562B1 (ko) * 2010-04-30 2012-04-05 한국표준과학연구원 비점수차 렌즈를 이용한 형상측정장치

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Cited By (37)

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Publication number Priority date Publication date Assignee Title
US8848502B2 (en) 1996-02-14 2014-09-30 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US6147955A (en) * 1996-02-14 2000-11-14 Samsung Electronics Co., Ltd. Optical pickup device to read from and record information to disks of different thicknesses
US6882614B2 (en) 1996-02-14 2005-04-19 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US6259668B1 (en) 1996-02-14 2001-07-10 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US5909424A (en) * 1996-02-14 1999-06-01 Samsung Electronics Co., Ltd. Optical pickup device and method to read from and record information to disks of different thicknesses
US20030002402A1 (en) * 1996-02-14 2003-01-02 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US8503272B2 (en) 1996-02-14 2013-08-06 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US20030193877A1 (en) * 1996-02-14 2003-10-16 Samsung Electronics Co., Ltd. Recording/reproducing apparatus having an optical pickup device to read from and record information to disks of different thicknesses
US6791933B1 (en) 1996-08-29 2004-09-14 Samsung Electronics Co., Ltd. Optical pickup using an optical phase plate
US7072114B2 (en) 1996-08-29 2006-07-04 Samsung Electronics Co., Ltd. Optical pickup using an optical phase plate and which is compatible with optical recording media of different types
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CN1077999C (zh) 2002-01-16
KR100269105B1 (ko) 2000-10-16
EP0777221B1 (de) 2003-09-10
JP3043287B2 (ja) 2000-05-22
EP0777221A1 (de) 1997-06-04
CN1158478A (zh) 1997-09-03
TW419103U (en) 2001-01-11
JPH09180245A (ja) 1997-07-11
DE69629899D1 (de) 2003-10-16
DE69629899T2 (de) 2004-05-13
MY117678A (en) 2004-07-31
KR970050310A (ko) 1997-07-29

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